JPH02125204A - Optical multiplexer/demultiplexer and its manufacture - Google Patents

Abstract

PURPOSE:To suppress insertion loss low and to accurately and easily perform alignment by forming a cut part in a main fiber, finishing the tip part of a branch optical fiber in a plate shape and inserting the tip part into the cut part, and inserting a wavelength selective film into this coupling part. CONSTITUTION:The core 21 of the main fiber 20 where incident light beam and transmitted light beam are propagated, the core 31 of the branch fiber 30 where reflected light beam is propagated, and the dielectric multilayered film of the wavelength selective filter 40 where the incident light beam is separated into the reflected light beam and transmitted light beam according to the wavelength cross one another at one point. Efficient optical multiplexing and demultiplexing are therefore performed and the alignment is easily carried out with high accuracy. Consequently, the insertion loss can be suppressed low and the optical multiplexer/demultiplexer capable of enabling the accurate and easy alignment, etc., is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical multiplexer/demultiplexer that demultiplexes or multiplexes light propagating in an optical fiber according to its wavelength, and a method for manufacturing the same. .

[Conventional technology]

Conventionally known optical multiplexer/demultiplexers can be categorized based on their structure: optical element type, optical fiber type, and waveguide type. Optical element type optical multiplexer/demultiplexer is, for example, ``Optical demultiplexer for bidirectional transmission'' (Proceedings of the 1981 National Conference of Electronic Communications and Computer Science Society of Japan, 815) and ``Diffraction grating type demultiplexer for two-wavelength bidirectional transmission.''"Single Mode Fiber Optical Multiplexer/Demultiplexer" (Proceedings of the 1986 Institute of Electronics, Information and Communication Engineers Spring National Conference C-472). This involves collimating light emitted from an optical fiber using a lens or the like, and inserting a dielectric multilayer film or a diffraction grating into the optical path. An example of an optical fiber type optical multiplexer/demultiplexer is a "single mode optical multiplexer/demultiplexer" (1988 Institute of Electronics, Information and Communication Engineers technical report EMC87-45).
is shown. This involves processing the end face, side surface, or midway of an optical fiber to perform multiplexing and demultiplexing of light. Further, a waveguide-type optical multiplexer/demultiplexer is shown, for example, in "Quartz-Based Optical Multiplexer/Demultiplexer" (Proceedings of the National Conference of the Institute of Electronics and Communication Engineers, 1988, 1.006). This multiplexes and demultiplexes light by using a guide wavepath formed on a silicon substrate.

Regarding optical fiber type optical multiplexers/demultiplexers, examples of those using wavelength selective filters made of dielectric multilayer films include ■, "Single mode optical multiplexer/demultiplexers" (1988 Institute of Electronics, Information and Communication Engineers Spring National Conference) Conference C-475), ■, “Wavelength division optical multiplexer/demultiplexer J for two-channel single mode transmission system
'WavelengthDivision Mul
ti DeIlultlplexers ['or T
wo-Channal Single-Mode
Transmission 5ysLei+5(JO
Ul? NAL 01' LICIITW^VE
TECIINOLOGY, Vol.

L'r-2, No, 5. October 1984), ■, “
"Low loss, low crosstalk single mode optical multiplexer/demultiplexer" (Proceedings of the 1986 Institute of Electronics, Information and Communication Engineers, Radio Division National Conference 309) is well known. Here, in the technique in the document (2) above, two dielectric multilayer films are used to make the output angle of the reflected light parallel to the transmitted light, and the side surfaces of the optical fibers are polished to polish the cores of both optical fibers. I'm trying to keep them close together. Also,
In the technique of the above-mentioned document (2), the side surfaces of the optical fibers are polished down to the core, thereby bringing the cores of both optical fibers into contact. Furthermore, in the technique of the above-mentioned document (2), the end face of an optical fiber is cut at a predetermined angle, and the end face is brought into contact with four parts formed on the side surface of another optical fiber.

[Problem to be solved by the invention]

In an optical fiber type optical multiplexer/demultiplexer using a dielectric multilayer film, light passing through the dielectric multilayer film propagates in the same straight direction as the incident light. On the other hand, the reflected light having a wavelength that is selectively reflected by the dielectric multilayer film is separated from the transmitted light at a predetermined angle with respect to the optical axis direction of the incident light. Therefore, the main fiber that propagates incident light and transmitted light and the branch fiber that propagates reflected light need to be arranged so as to intersect at a predetermined angle. In addition, in order to keep the loss (especially the insertion loss of reflected light) caused by inserting a branch fiber into the main fiber from the side as low as possible, the cores of the main fiber and branch fiber should be placed as close to each other as possible, and the It is necessary to shorten the distance.

In order to meet the above requirements, the techniques described in the above-mentioned documents (1) to (3) have been proposed, but no matter which method is used, delicate alignment must be performed.

There is also the problem of requiring high precision in position and angle.

Therefore, the present invention provides an optical multiplexer/demultiplexer that can suppress insertion loss to a low level and that can perform alignment etc. easily and accurately.
It is an object of the present invention to provide a manufacturing method with a high yield.

[Means to solve the problem]

In the optical multiplexer/demultiplexer according to the present invention, a branch fiber is coupled to a main fiber from an oblique direction, and a wavelength-selective filter is provided at this coupling part so as to cross the main fiber, so that a wavelength-selective filter is provided to cross the main fiber. In an optical multiplexer/demultiplexer, the light transmitted through the wavelength selective filter is propagated to the other side of the main fiber, and the light reflected by the wavelength selective filter is propagated to the branch fiber. A notch extending from the joining direction to at least the core of the main fiber is formed, and the end of the branched fiber on the joining side has a thickness equal to the width F of the notch and includes the core of the branched fiber. The plate-shaped joint end is finished and the plate-like joint end is inserted into the notch.

Further, in the optical multiplexer/demultiplexer according to the present invention, in the above structure, the main fiber and the branch fiber are fixedly installed in the V-shaped groove formed on the substrate, and the wavelength selective filter is provided in the main fiber 7.
The filter may be inserted and fixed into a filter insertion groove formed in the substrate at the same position as the notch of the fiber.

Further, in the manufacturing method according to the present invention, a main groove and a branch groove that intersect from an oblique direction are formed on a substrate, and then a main fiber is fixed in the upper groove, and at least a core portion of the main fiber is separated by a predetermined width from the direction of the branch groove. A notch extending up to The end portion is fixed in the branch groove so as to be inserted into the notch, and then the joint portion of the main fiber and the branch fiber is cut to form a filter insertion IFi portion that reaches a predetermined depth of the substrate, and then A wavelength selective filter is inserted and fixed in the filter insertion groove.

[Effect]

According to the optical multiplexer/demultiplexer of the present invention, a notch is formed in the main fiber, the distal end of the branched fiber is finished into a plate shape, and the main fiber can be connected by simply inserting this plate-shaped coupling end into the notch. and the core of the branched fiber are contacted. Therefore, by forming a filter insertion groove in this coupling portion and inserting a wavelength selective filter, a highly efficient optical multiplexer/demultiplexer can be realized.

Furthermore, according to the manufacturing method of the present invention, the cut portion of the main fiber and the filter insertion groove can be formed while the optical fiber is fixed to the Wk, so that an optical multiplexer/demultiplexer can be realized with high yield.

〔Example〕

The present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view showing the configuration of an optical multiplexer/demultiplexer according to an embodiment, and FIG. 2 is a diagram illustrating its planar configuration and operation. As shown in FIG. 1, a main groove 11 with a linear cross section is formed on the upper surface of the substrate 10, and a branch groove 12 with a V-shaped cross section intersects with the main groove 11 at an angle 2θ. It is formed. A filter insertion groove 13 is formed across the intersection of the main groove 11 and the branch groove 12. On the other hand, the main fiber 20 is cut diagonally at a predetermined angle 2θ at the joint portion, and this portion forms a cut portion 22 . The distal end of the branched fiber 30 is finished into a plate-shaped coupling end 32 that includes a core '31, and this plate-shaped coupling end 32 is inserted into the IuJ recess 22 of the main fiber 20. Then, at the portion where the core 21 of the main fiber 20 and the core 31 of the branch fiber 30 contact, the main fiber 20
The branch fiber 30 is cut, and a wavelength selective filter 40 is inserted therein. Here, the angle at which the main groove 11 and the branch '1ml 2 intersect and the angle at which the main fiber 20 and the branch fiber 30 intersect are the same (both 2θ
), the main fiber 20 and the branch fiber 30
are fixed to the main groove 11 and the branch groove 12, respectively +I
At this time, the wavelength selective filter 40 is inserted into the filter insertion groove 13 and can be identified.

With reference to FIG. 2(b), the configuration near the coupling portion will be explained in more detail. A main fiber 20 is fixed in the main groove 11 of the substrate 10 with a contact agent or the like. In this state, a cut portion 22 having a width d1+α along the direction of the branch groove 12 is formed in the main fiber 20. On the other hand, the tip of the main fiber 20 is connected to a plate-shaped coupling end 32, and the thickness dl of this plate-shaped coupling end 32 is slightly smaller than the width of the notch 22 (
αtake) is getting smaller. And branch fiber 30
is fixed in the branch groove 12 with an adhesive or the like, and a refractive index matching liquid (matching oil) or a bonding agent for refractive index matching is applied between the notch 22 and the plate-shaped joint end 32. is fulfilled.

In this way, when the filter insertion groove 13 is formed in the substrate 10 with a width d2+β with the main fiber 20 and the branch fiber 30 fixed to the base 10, the main fiber 20 and The coupling portion of the branched fiber 30 is cut.Then, a wavelength selective filter 40 having a width d2 is inserted into this filter insertion groove 13.The wavelength selective filter 40 has a glass substrate 41 attached thereto. For example, the wavelength λ1-1.3
It is configured to transmit light with a wavelength of 7 zm and reflect light with a wavelength of λ2-1.55 μm. The wavelength selective filter 40 is fixed in the filter insertion groove 13 with an adhesive or the like, and the space between the main fiber 20 and the branch fiber 30 is filled with the above-mentioned matching oil or the like.

Next, the operation of the above embodiment will be explained with reference to FIGS. 2(a) and 2(b).

When the incident light (A1, λ) propagates into the core 21 of the main fiber 20, the light with a wavelength of λ1-1.3 μm passes through the wavelength selective filter 40 and continues through the main fiber 20, and is combined with the transmitted light. Becoming and propagating [7. On the other hand, light with a wavelength of λ2-1.55 μm is reflected by the dielectric multilayer film 42 of the wavelength selective filter 40 and is reflected by the core 3 of the branch fiber 30.
1 as reflected light. At this time, the incident angle and the outgoing angle of the incident light with respect to the wavelength selective filter 40 are J( and θ), and the relationship is as shown in FIG. 2(a).

In the present invention, the core 21 of the main fiber 20 propagates incident light and transmitted light, and the branch fiber 30 propagates reflected light.
The core 31 and the dielectric multilayer film 42 of the wavelength selective filter 40 that separates incident light into reflected light and transmitted light according to the wavelength intersect at the - point. Therefore, it is possible to perform extremely efficient optical multiplexing and demultiplexing. Also,
Alignment can be performed extremely easily and with high precision.

Next, the manufacturing process of the above optical multiplexer/demultiplexer will be explained with reference to FIGS. 3 to 7.

First, a substrate 10 made of silicon single crystal is prepared, and a third
Form a groove as shown in the figure. Chemical etching of silicon may be used to form the grooves, but the grinding depth accuracy is 0.5.
A processing device (not shown) on the order of μm may be used. Using this, main grooves 11 and branch grooves 12 that intersect at an angle of 2θ are formed in the substrate 10. In addition, 2 parallel to the branch groove 12
700. The side grooves 13a, 13b of the book. They are formed to have an interval of about czm -C71=600 .mu.rn and a width of about 300 .mu.m.

These side grooves 138, 13b are for preventing the adhesive from flowing out when fixing the optical fiber, and their function will be described later with reference to FIG.

Next, the main fiber 20 is set in the main groove 11 on the substrate 10. As the main fiber, for example, an 11-mode optical fiber having an outer diameter of 125 μm and a core diameter of 10 μm may be used, but it is not limited to this. Fixed at 11.

Here, the location to be fixed using the epoxy adhesive is the part indicated by symbols At and A2 in FIG.
a.

Do not put epoxy adhesive into the inner part of 1'3b.

In this way, the epoxy adhesive in the A1 and A2 portions will not flow into the joint portion (the intersection of the main groove 11 and the branch groove 12) on the inner side due to the presence of the side grooves 13a and 13b. Therefore, when the branched fibers are later fixed, there will be no problem such as the presence of a contacting agent in the groove.

Next, a cut portion 22 is formed in the main fiber 20 using a grinding blade 81 having a thickness of approximately 30 μm.

This notch 22 is in the same direction as the branch groove 12,
As a result, the main fiber 20 is separated into a part for propagating incident light (the left part in the figure) and a part for propagating transmitted light (the right part in the figure). Since this separation process is performed with the main fiber 20 fixed in the main groove 11 of the substrate 10, there is no misalignment of the two fibers, and hence no subsequent alignment work is required.

Next, a branched fiber 30 whose tip end is finished into a plate-like joint end portion 32 is produced. The branched fiber 30 is processed by setting the branched fiber 30 on the substrate of a grinding device (not shown), waxing it, and scraping off the cladding portion at the tip with a grinding blade to form a plate with a thickness of about d2-20 μm. This can be achieved by Note that it is preferable to use a single-mode optical fiber similar to the main fiber 20 for the branch fiber 30.

The wax is removed from the branched fiber 30 thus produced, and the branched fiber 30 is set as shown in FIG.

That is, the plate-like coupling end 32 is inserted into the notch 22, the branch fiber 30 is set in the branch groove 12, and fixed with an epoxy adhesive. At this time, if side grooves (not shown) similar to the side grooves 13a and 13b are provided in the main groove 11 and the hand side, the epoxy-based rock contact agent for fixing the branched fiber 30 can be attached to the main fiber 20. This can prevent the fibers from flowing into the joints of the branched fibers 30.

What is important here is that the branch fiber 30 and the main fiber 2
0 can also be aligned easily with extremely high accuracy. That is, the incident light portion and the transmission destination portion of the main fiber 20 are aligned by fixing the main fiber 20 in the main groove 11 and cutting it, but also regarding the alignment of the main fiber 20 and the branch fiber 30, By fixing the branching fiber 30 to the branching groove 12, this can be done easily and with high precision. This is because the main groove 11 and the branch groove 12 are V-shaped grooves of the same size and shape, and the main fiber 20 and the branch fiber 30
This is because they have the same size, and the plate-like coupling end 32 of the branched fiber 30 includes the core 31.

Note that when the main fiber 20 and the branch fiber 30 have different sizes, the main groove 11 and the branch groove 12 may have different sizes and shapes. In the above manner, the input fiber,
The three core parts of the transmission fiber and the reflection fiber are -
Since the points are in contact with or close to each other, the insertion loss is significantly reduced.

Next, as shown in FIG. 5, the joint portion of the main fiber 20 and the branch fiber 30 is cut and analyzed by a cutting blade 82 having a thickness of approximately 50 μm, and a filter insertion groove 13 is formed in the JJ plate 10. It is formed at a depth of 11 m. The direction of this filter insertion groove 13 must be as shown in FIG. 2(a).
The direction of the dummy grooves 14a, 1. as shown in FIG.
4b, 15a.

This can be easily realized by forming 15b. That is, two dummy grooves 14a and 14b in 14 rows are formed in the main groove 11 at an interval of about 20 nil from the main groove 11, and at the same time, two dummy grooves 14a and 14b are formed at an interval of about 20 nil from the branch groove 12. Two dummies 1m descending to the branch groove 12 15
form a, 15 b. And Dami 1M14
The filter insertion groove 13 is formed as shown in FIG. 5 along a line (dotted line in the figure) connecting the intersection P1 of the dummy grooves 14b and 15a and the intersection P2 of the dummy grooves 14b and 15b. Then, the filter insertion groove 13 is formed at the position where the core 21 of the main fiber 20 and the core 31 of the branched fiber 30 intersect.

Next, the wavelength selective filter 40 is manufactured. This wavelength selective filter 40 has a dielectric multilayer film 42 on a glass plate 41.
It is obtained by forming the glass plate 41 by a vacuum evaporation method or the like, and then polishing the glass plate 41 to make it thin. Next, such a wavelength selective filter 40 (thickness: 40 μm) is inserted into the filter insertion groove 13 as shown in FIG. Then, the optical multiplexer/demultiplexer is completed by fixing the gap with epoxy adhesive and filling the gap with matching oil.

In this invention, by going through a series of steps, the cores of the main fiber 20 and the branch fiber 3o intersect with the wavelength selective filter 40 at one point. Therefore, the insertion loss can be significantly reduced (1) and the circumference can be extremely simple.

Various modifications are possible to the present invention.

For example, the cut in the main fiber is not limited to cutting the main fiber, but as long as the cut is deep enough to reach at least the core of the main fiber, the plate-shaped joint end of the branch fiber can be inserted to bring both cores into contact. It is possible to do so. Further, the optical fiber is not limited to a single mode type, but may be a multimode type.

〔Effect of the invention〕

As explained in detail above, in the present invention, a notch is formed in the main fiber, the tip of the branch fiber is finished in a plate shape,
The cores of the main fiber and the branch fiber are brought into contact with each other by inserting this plate-like joint end into the cut. Therefore, by forming a filter insertion groove in this joint and inserting a wavelength selective filter, insertion loss can be kept low.
Furthermore, it is possible to realize an optical multiplexer/demultiplexer that can perform one rotation center, etc. with an accuracy of <lI'l'141.

Further, according to the manufacturing method of the present invention, the cut portion of the main fiber and the filter insertion groove can be formed while the optical fiber is fixed to the substrate, so that an optical multiplexer/demultiplexer can be realized with high yield.

Therefore, the present invention can be used for injecting and extracting pulsed light for line maintenance into and out of lines in fields such as optical communications. It can also be used to inject and discharge pump light in optical amplification using Raman scattering, Prillouin scattering, etc. in communication lines. This is because the application of the optical multiplexer/demultiplexer to such fields requires reduction of insertion loss of signal light and highly efficient multiplexing and demultiplexing of monitor light.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of an optical multiplexer/demultiplexer according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the planar configuration and operation of the embodiment, and FIGS. 3 to 7 are an exploded perspective view of an optical multiplexer/demultiplexer according to an embodiment of the present invention. It is a perspective view by process which shows one Example of the manufacturing method of a corrugated device. 10...J! Plate, 11... Main groove, 12... Branch groove, 13... Filter insertion groove, 13a, 13b... Side groove, 20... Main fiber, 21... Core, 30...
Branch fiber 31... Core, 32... Plate-like coupling end, 40... Wavelength selective filter, 42... Dielectric multilayer film.

Claims (1)

[Claims] 1. A branch fiber is coupled to the main fiber from an oblique direction, and a wavelength selective filter is provided at this coupling part so as to cross the main fiber, so that the branch fiber is coupled to the main fiber from one side of the main fiber. In the optical multiplexer/demultiplexer, the light transmitted through the wavelength selective filter is propagated to the other side of the main fiber, and the light reflected by the wavelength selective filter is propagated to the branch fiber, The main fiber is formed with a notch extending from the coupling direction of the branch fibers to at least the core of the main fiber, and the tip of the branch fiber on the coupling side has a thickness less than or equal to the width of the cut. An optical multiplexer/demultiplexer characterized in that the plate-like coupling end portion is finished into a plate-shaped coupling end portion including a core portion of the branched fiber, and the plate-shaped coupling end portion is inserted into the cut portion. 2. The main fiber and the branch fibers are fixedly installed in a V-shaped groove formed on the substrate, and the wavelength selective filter is installed in a filter insertion groove formed in the substrate at the intersection of the main fiber and the branch fiber. 2. The optical multiplexer/demultiplexer according to claim 1, wherein the optical multiplexer/demultiplexer is inserted into and fixedly installed in the optical multiplexer/demultiplexer. 3. A first step of forming a main groove and a branch groove intersecting from an oblique direction on the substrate, and fixing the main fiber in the main groove and forming at least one of the main fibers with a predetermined width from the direction of the branch groove. a second step of forming a notch in the main fiber that extends to the core; and a second step in which the tip end has a thickness less than the width of the notch and is finished into a plate-like joint end including the core. a third step of fixing a branch fiber in the branch groove such that the plate-like joint end portion is inserted into the cut portion; and cutting the joint portion between the main fiber and the branch fiber; An optical multiplexing method comprising: a fourth step of forming a filter insertion groove that reaches a predetermined depth in the substrate; and a fifth step of inserting and fixing a wavelength selective filter into the filter insertion groove. A method of manufacturing a duplexer.